Re: [PATCH v6 6/6] list-objects-filter: implement filter tree:0

At the risk of going on a tangent, I assumed this was because enums
are really ints, and the "default" is there in case the enum somehow
got assigned to an int without a corresponding value. Either because
of a cast from an int that was out-of-range, or new values that were
obtained from arithmetic or bitwise operations on the declared enum
values, which created undeclared values.

See
374166cb381 (grep: catch a missing enum in switch statement, 2017-05-25)
or a bit date, but nevertheless an interesting read:
b8527d5fa61 (wt-status: fix possible use of uninitialized variable, 2013-03-21)

...compilers these days are just too smart to reason about them :-)